The infrared spectrum of propyne in the range 6200-6700 cm−1

► The absorption spectrum of CH3CCH was investigated in the range 6200-6700 cm−1. ► Conventional FTIR, FTIR using femtosecond source and CRDS were used. ► One perpendicular and four parallel bands, all perturbed, were analyzed. ► A Hamiltonian with all symmetry allowed perturbations between upper levels was built. ► In total 1176 rovibrational transitions have been assigned and simultaneously fitted.